If you had said 3.5 GB, I would have my doubts, but 3 GB to 4 GB is a sensible jump that should more than make up for the slightly less compact x64 code and data structures it creates. x64 also has more registers, which I suppose should make it faster? Complete speculation, of course. Realistically, I don't expect to see any difference; it's just not "right" to let 1 GB sit unused, and deny yourself the ability to run 64-bit software (which then again, is not a significant concern as most common software still comes in 32-bit flavors).